Documentation of Salted Paper Prints with a Modified Digital Camera

ABSTRACT A modified digital camera can be used for photographic techniques that utilize not only the visible light spectrum but longwave ultraviolet and near-infrared radiation. Seven techniques were used to document salted paper prints: visible light photography with normal, raking, and specular illumination, UVA-induced visible fluorescence, reflected UVA, reflected near-IR, and visible-induced infrared luminescence. The last four techniques, in particular, can reveal or accentuate subtle differences in materials or condition issues of salted paper prints that may otherwise be hard to discern in visible light. In order to achieve consistency, a standardized workflow was created taking into consideration several important factors, such as light and radiation sources, setup, lens choice, use of filters, and incorporating target references for color rendering, exposure control, and image processing procedures. An exposure sequence is suggested to safeguard the prints and to increase efficiency. Total exposure was monitored to ensure that light and UVA exposure during documentation did not induce detectable change.